Formate Brines for Drilling and Completion: State of the Art

Howard, Siv

doi:10.2523/30498-ms

Cited by 43 publications

(33 citation statements)

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“…All of these reactions are reversible so that formate and formic acid can be generated by reduction of dissolved CO 2 or HCO 3 with hydrogen 27 by hydration of CO. At equilibrium, the formate to CO 3 2-/ HCO 3 -/ CO 2 ratio depends on the pH of the solution. More formate / formic acid is favored at higher pH.…”

Section: Theory Of Formate Decompositionmentioning

confidence: 99%

Hydrothermal Chemistry of Formate Brines and Its Impact on Corrosion in HPHT Wells

Howard

Downs

2008

All Days

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Formate brines have been successfully used in hundreds of HPHT drilling and completion operations over the past 12 years and have exhibited remarkable thermal stability. This has been confirmed by analyses of brines recovered from extreme HPHT wells after lengthy exposure (months/years). Laboratory testing cited in the literature has, however, indicated that significant formate brine decomposition to bicarbonate and hydrogen gas should occur at even relatively low temperatures if the brine is in contact with catalytic surfaces. The potential damage that such decomposition and the evolution of decomposition products could cause to metallic materials has caused concern in the industry.The inconsistency between laboratory and field behavior has indicated that standard laboratory autoclaves are not suited for reproducing or simulating downhole conditions. Typical differences between these two environments are pressure, presence of gas cap, and amount and type of catalytic surfaces. In order to better simulate actual downhole conditions, experiments have been carried out in specialist equipment developed to examine hydrothermal chemistry. A non-catalytic gold test cell was used for the decomposition testing, immersed in a high pressure high temperature autoclave filled with water.The flexibility of the gold cell has allowed experiments to be conducted and sampled at high pressure without the presence of an artificial gas cap. Initial tests have shown that any decomposition reactions taking place in formate brine under hydrothermal conditions will reach equilibrium with bicarbonate. This discovery has also given us useful information on how to formulate bicarbonate-rich formate brine compositions which remain stable even at very high temperatures. As bicarbonate is an important component in buffered formate brines, these formulations are not much different from the current brines already in field use.Analyses of a range of formate brine samples that have been recovered from two HPHT wells have confirmed that formate reaches equilibrium with bicarbonate over time under hydrothermal conditions.This paper reviews what has been learnt about formate decomposition under realistic hydrothermal conditions, and exposes new information on how the equilibrium reactions might impact on metal integrity and corrosion processes in HPHT wells.The most important lesson learned from testing in the flexible gold cell is that traditional laboratory autoclaves operated with a gaseous head space are not suited for testing formate brines at high temperatures. In fact, test results generated in such autoclaves will be laboratory artifacts that do not simulate or reproduce what actually happens in HPHT wells.

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Section: Theory Of Formate Decompositionmentioning

confidence: 99%

Hydrothermal Chemistry of Formate Brines and Its Impact on Corrosion in HPHT Wells

Howard

Downs

2008

All Days

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“…Formate salts are recognized for their ability to reduce polymer degradation at temperatures above conventional operating pressures. 2,3,4 This property has been used to design high-temperature drilling fluids for operations in other parts of the world, specifically the United Arab Emirates, Central Europe and the North Sea. 5,6 Despite the higher cost of the brine, these fluids in many cases have proven to be more economical overall, as chemical consumption is greatly reduced due to the improvement in thermal stability.…”

Section: Base Fluid Selectionmentioning

confidence: 99%

Reservoir Drilling Fluids-Designing for Challenging Wells in a Remote Location

Knox¹,

Bradshaw²,

Svoboda³

et al. 2005

Proceedings of SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Belanak A platform is situated in the Natuna Sea region of Indonesia. The reservoir sections are high temperature (315°F BHST), and the openhole sections were planned to be between 3500 and 4500 ft horizontal, some with tortuous well paths required to meet the target. In order to ensure excellent drilling performance and optimum protection of the producing formation, a formate-based, low-solids reservoir drilling fluid was selected -the first time such a system had been used in Indonesia.In this paper, the authors detail the design and successful application of the unique reservoir drill-in fluid in the demanding and remote well.

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“…[4][5][6][7][8][9][10][11][12][13] The implementation of such fluids has become an accepted best practice within the petroleum industry. Commonly referred to as reservoir drilling fluids (RDF) or drill-in fluids, these particular formulations are specifically designed to help prevent formation damage, minimize rig time, and provide maximum production efficiency.…”

Section: Introductionmentioning

confidence: 99%

New Filtration-Control Polymer for Improved Brine-Based Reservoir Drilling-Fluids Performance at Temperatures in Excess of 400°F and High Pressure

Ezell

Ezzat

Turner

et al. 2010

SPE International Symposium and Exhibition on Formation Damage Control

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Brine-based reservoir drilling fluids are a special class of fluids designed to minimize formation damage, provide the necessary hole cleaning, help reduce wellbore cleanup time and cost, and allow reservoirs to be produced to the maximum of their potential. These fluids should address the wide range of difficulties frequently encountered in horizontal drilling, completion, and workover operations. Filtration control chemicals for currently available drill-in fluid systems exposed to extremely high bottomhole temperatures and pressure conditions are not effective or stable for drilling long horizontal sections of the reservoir. Failure to secure a low filtration rate and thin wallcake causes stuck pipe and loss of expensive downhole tools.Conventional fluid loss control additives for high performance brine-based drill-in fluids include nonionic water soluble polymers, such as starches, derivatized starches, gums, derivatized gums, and cellulosics. Cross-linked starches are often considered the benchmark of performance for utilization in reservoir fluids, but they do not have the thermal stability required for successful deployment at temperatures exceeding 300°F for extended contact periods.Conventional linear synthetic polymers are also utilized, but oftentimes they require another additive, such as phyllosilicate particles, to be able to effectively function as fluid loss control additives. The use of clay can be problematic in drill-in fluids, as removing the clay from the formation can be difficult because it infiltrates into pores. Furthermore, the addition of the linear synthetic polymers dramatically increases the viscosity of the fluid, which can result in increased equivalent circulating densities (ECD) and decreased drilling rates.Through advanced synthetic polymer techniques, a novel polymeric fluid loss control additive has been developed for brine-based reservoir drill-in and completion fluids. The new polymer provides enhanced thermal stability to temperature in excess of 400°F in monovalent and divalent halide brines. This paper presents detailed fluid formulations and discusses the polymer evaluation data under simulated downhole HPHT conditions.

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Formate Brines for Drilling and Completion: State of the Art

Cited by 43 publications

References 0 publications

Hydrothermal Chemistry of Formate Brines and Its Impact on Corrosion in HPHT Wells

Hydrothermal Chemistry of Formate Brines and Its Impact on Corrosion in HPHT Wells

Reservoir Drilling Fluids-Designing for Challenging Wells in a Remote Location

New Filtration-Control Polymer for Improved Brine-Based Reservoir Drilling-Fluids Performance at Temperatures in Excess of 400°F and High Pressure

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